Method and apparatus for bringing laser chips to a measurement position

ABSTRACT

An apparatus for measuring output light intensity from laser chips mounted on respective carriers on a fixture, comprises a control unit for moving the fixture to in turn bring the chips to a measurement station, and a TV camera and a NIR camera both connected to a vision system for determining x and y coordinates of objects viewed by the TV camera and the NIR camera, respectively. The control unit is adapted to move the fixture to bring the respective chip in front of the TV camera to determine the coordinates of the chip on the fixture, move the fixture in response to the coordinates of the chip on the fixture to bring the chip in front of the NIR camera to determine the coordinates of a point of maximum light intensity from the ignited chip, and move the fixture in response to the coordinates of the point of maximum light intensity to bring the chip to the measurement station.

TECHNICAL FIELD

The invention relates generally to laser chips and more specifically toa method and an apparatus for bringing a population of manufacturedlaser chips to a measurement position to select good laser chips, i.e.laser chips that fulfil an output light intensity requirement.

BACKGROUND OF THE INVENTION

Manufactured laser chips are mounted on carriers. To test whether or notthe laser chips fulfil the requirement on output light intensity, thecarriers with the chips are placed on a fixture that is moved to in turnbring the chips to a measurement station. This is a time consumingprocess in that the location of the point of maximum output lightintensity of a laser chip on a carrier is unknown. Therefore, at themeasurement station, each chip has to be scanned in order to locate thepoint of maximum output light intensity before the light intensity canbe measured. If for some reason a chip is missing in its expectedposition on the fixture, the scanning for the point of maximum outputlight intensity for that chip can continue until an operator notices thesituation.

SUMMARY OF THE INVENTION

The object of the invention is to more quickly locate the point ofmaximum output light intensity of laser chips on carriers on a fixture.

This is attained by the method according to the invention of measuringoutput light intensity from laser chips mounted on respective carrierson a fixture, comprising moving the fixture to in turn bring the chipsto a measurement station in that, for each chip, the fixture is firstmoved to bring the chip in front of a TV camera connected to a visionsystem that is adapted to determine x and y coordinates of objectsviewed by the TV camera, the coordinates of the chip on the fixture aredetermined by means of the vision system, the fixture is then moved inresponse to the coordinates determined by the vision system to bring thechip in front of a NIR camera connected to the vision system that isadapted to determine also x and y coordinates of objects viewed by theNIR camera, the laser chip is ignited, and the x and y coordinates ofthe point of maximum light intensity from the chip are determined bymeans of the vision system, whereupon the fixture is moved in responseto the determined coordinates of the point of maximum light intensity tobring the chip to the measurement station to measure the lightintensity.

This is also attained by the apparatus according to the invention formeasuring output light intensity from laser chips mounted on respectivecarriers on a fixture, comprising a control unit for moving the fixtureto in turn bring the chips to a measurement station (3), a TV camera anda NIR camera both connected to a vision system for determining x and ycoordinates of objects viewed by the TV camera and the NIR camera,respectively. The control unit is adapted to move the fixture to bringthe respective chip in front of the TV camera to determine thecoordinates of the chip on the fixture, move the fixture in response tothe coordinates of the chip on the fixture to bring the chip in front ofthe NIR camera to determine the coordinates of a point of maximum lightintensity from the ignited chip, and move the fixture in response to thecoordinates of the point of maximum light intensity to bring the chip tothe measurement station.

By the method and the apparatus according to the invention, the processof locating the point of maximum output light intensity of laser chipson carriers on a fixture will be much quicker than the processes usedtoday.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of an embodiment of an apparatusaccording to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of an apparatus forbringing laser chips 1 mounted on respective carriers 2 to a measurementstation 3 to measure output light intensity of the chips 1.

In a manner known per se, the carriers 2 with the chips 1 are mounted ona fixture 4, and the fixture 4 is moved to in turn bring the chips 1 tothe measurement station 3.

In the embodiment shown, the fixture 4 is driven by means of a motor(not shown), e.g. a linear motor, along a rod 5 under control of acentral control and signal processing unit 6.

In accordance with the invention, the fixture 4 is first moved along therod 5 to bring the first chip 1 in front of a TV camera 7. The TV camera7 is connected to a vision system 8 that is adapted to determine x and ycoordinates of objects viewed by the TV camera 7, and that is connectedto the central control and signal processing unit 6.

By means of the vision system 8, the coordinates of the chip 1 on thefixture 4 is determined and transferred to the central control andsignal processing unit 6.

If a chip is missing on the fixture, this is detected by the visionsystem and the fixture is moved to bring the next chip in front of theTV camera.

In response to the coordinates determined by the vision system 8, thecentral control and signal processing unit 6 controls the motor (notshown) to move the fixture 4 such that the chip 1 is brought in front ofa near infra-red (NIR) camera 9. The NIR camera 9 is also connected tothe vision system 8 that is adapted to determine x and y coordinates ofobjects viewed by the NIR camera 9.

In accordance with the invention, the laser chip 1 is now ignited, andthe x and y coordinates of the point of maximum light intensity from thechip 1 as viewed by the NIR camera 9 is now determined by means of thevision system 8.

In response to the determined coordinates of the point of maximum lightintensity, the fixture 4 is moved such that the chip 1 is brought to themeasurement station 3 to measure the light intensity.

The measurement station 3 can be e.g. an optical fibre connected to aninput terminal of the central control and signal processing unit 6.

Depending on whether the maximum light intensity of the chip 1 is aboveor below a predetermined threshold, the chip 1 is accepted or discarded.

As should be apparent from the above, it is not necessary to scan a“window” in order to locate the point of maximum light intensity of achip and, consequently, the apparatus according to the invention isquicker than the apparatuses known so far.

1. A method of measuring output light intensity from laser chips mountedon respective carriers on a fixture, comprising the steps of: moving thefixture to in turn bring the chips to a measurement station; wherein,for each chip, moving the fixture to bring the chip in front of a TVcamera connected to a vision system for determining x and y coordinatesof objects viewed by the TV camera; determining the coordinates of thechip on the fixture by means of the vision system; moving the fixture inresponse to the coordinates of the chip on the fixture to bring the chipin front of a NIR camera connected to the vision system for determiningx and y coordinates of objects viewed by the NIR camera; igniting thelaser chip; determining the coordinates of a point of maximum lightintensity from the chip by means of the vision system; and moving thefixture in response to the coordinates of the point of maximum lightintensity to bring the chip to the measurement station to measure thelight intensity.
 2. An apparatus for measuring output light intensityfrom laser chips mounted on respective carriers on a fixture comprising;a control unit for moving the fixture to in turn bring the chips to ameasurement station; a TV camera; a NIR camera both connected to avision system for determining x and y coordinates of objects viewed bythe TV camera and the NIR camera, and that the control unit is adaptedto move the fixture to bring the respective chip in front of the TVcamera to determine the coordinates of the chip on the fixture, move thefixture in response to the coordinates of the chip on the fixture tobring the chip in front of the NIR camera to determine the coordinatesof a point of maximum light intensity from the ignited chip, and movethe fixture in response to the coordinates of the point of maximum lightintensity to bring the chip to the measurement station.
 3. The apparatusaccording to claim 2, wherein the measurement station, the TV camera andthe NIR camera are arranged along a rod on which the fixture is moved.4. The apparatus according to claim 3, further comprising a motor todrive the fixture along the rod.
 5. The apparatus according to claim 4,wherein the motor is a linear motor.